In the past I have succeeded in accessing a Google App Engine Datastore from a Google App Engine (GAE) application with Objectify and generating an Objective-C client for this application (including its Objectify Java annotations) with Google Cloud Endpoints. This gave me a client for accessing this datastore from iOS apps.
While initially some business logic did reside in the GAE application it has by now become just a facade for the datastore. With Google Clould Datastore it should therefore be possible to bypass the application (API backend) and access the datastore directly from iOS apps.
However, I can't find an Objective-C (or Swift) client in Google APIs Client Library for Objective-C. Is there none (above the level of "raw" REST calls) because the Cloud Datastore API is beta, or am I miscomprehending the larger picture?
UPDATE From reading this answer it occurs to me that the API backend may remain desirable from a security point of view, because that way iOS apps don't have to become privy to service accounts: those are kept servers-side. (I need to access the "app's", not the users' datastores.)